Re: [RFC PATCH 2/3] efi/loongarch: Randomize kernel preferred address for KASLR

[hev]

Hi Lisa,

On Mon, Apr 27, 2026 at 1:08 PM Lisa Robinson <lisa@bytefly.space> wrote:
>
> Hi Rui
>
> > diff --git a/drivers/firmware/efi/libstub/loongarch.c b/drivers/firmware/efi/libstub/loongarch.c
> > index 9825f5218137..80ba7d69e1b3 100644
> > --- a/drivers/firmware/efi/libstub/loongarch.c
> > +++ b/drivers/firmware/efi/libstub/loongarch.c
> > @@ -38,6 +38,21 @@ static efi_status_t exit_boot_func(struct efi_boot_memmap *map, void *priv)
> >       return EFI_SUCCESS;
> >  }
> >
> > +unsigned long efi_get_kimg_kaslr_address(void)
> > +{
> > +     unsigned int random_offset = 0;
> > +
> > +#ifdef CONFIG_RANDOMIZE_BASE
> > +     if (!efi_nokaslr) {
> > +             efi_get_random_bytes(sizeof(random_offset), (u8 *)&random_offset);
> > +             random_offset ^= (rdtime_l() << 16);
>
> random_offset &= ~(efi_get_kimg_min_align() - 1);

Thanks for pointing that out.

Aligning to 64K here seems preferable. Otherwise, it reduces the entropy.

Thanks,
Rui


>
> > +             random_offset &= (CONFIG_RANDOMIZE_BASE_MAX_OFFSET - 1);
> > +     }
> > +#endif
> > +
> > +     return PHYSADDR(VMLINUX_LOAD_ADDRESS) + random_offset;
> > +}
> > +
> >  unsigned long __weak kernel_entry_address(unsigned long kernel_addr,
> >               efi_loaded_image_t *image)
> >  {
>
> --
> Lisa